1. Field of the Invention
This invention most generally relates to a chain guide pulley/ derailleur pulley for use, generally in pairs, with a bicycle rear derailleur system. The chain guide pulley has teeth having a thickness dimension which allows for an acceptable amount of misalignment of the pulley relative to a drive chain and a selectable rear sprocket of a free wheel cluster of a multi-speed bicycle. More particularly the chain guide pulley has a number of holes between the outer periphery and a bearing upon which low resistance rotation is provided. These holes/apertures are not only effective to reduce the weight of the pulley, a very important consideration for bikers, but surprisingly these apertures improve, enhance and promote, while the bicycle is in use, the clearance of debris that tends to collect on currently used derailleur pulleys. For mountain bicycles this feature is of exceptional value and importance.
2. Description of the prior Art
Pulleys currently used as a part of drive chain rear derailleur assemblies have not had much consideration relative to providing improved performance. Most of the present pulleys use a rotational bearing system which allows for the lateral play of the toothed portion of the pulleys. This play is needed so that misalignments between the drive chain and the selected rear sprocket from which the chain is being guided from and also onto to change speeds do not result in inconsistent and inaccurate shifting. Pulleys using precision bearings which have no lateral play require continual or frequent adjustment and alignment of the shifting system in order to keep the rear derailleur functioning reliably and accurately.
In riding bicycles off-road or in mountainous and muddy/dirty terrain, debris or dirt/mud collects on the components of the speed changing system. This collection of debris also occurs on the derailleur guide pulleys of the rear derailleur assembly causing inconsistency in shifting and excessive wear. This problem with guide pulleys has not been addressed in any of the presently used pulleys known to the inventor hereof.
It would be advantageous to have a guide pulley or pulleys for use with bicycle derailleur systems having all of the particular objectives, features and advantages of: 1) Being strong and light in weight; 2) Being very low in rotational friction losses; 3) Compatibility with existing derailleur mechanisms or systems; 4) Having a tooth geometry which allows for an amount of misalignment of the derailleur and the gear cluster assembly providing thereby consistent and reliable speed changing using the derailleur mechanism; and 5) Special construction adaptable to cause debris collected onto the derailleur pulley to be constantly and easily removed and cleaned or cleared as a consequence of it being in use by the normal rotation thereof.
There is nothing currently available which satisfies these needs and objectives. However, this invention is particularly directed to an improved derailleur pulley or drive chain guide pulley which satisfies the objectives of a guide pulley which when used with conventionally known rear derailleurs for bicycles provides for an effective and reliable smooth speed change by lateral transfer of the drive train from any one rear sprocket to any other of the rear sprockets of the multi-gear rear cluster.
After reviewing patents which were developed in a search, no structure similar to the present invention was found nor was one suggested. None of the prior art known to the inventor hereof satisfies the needs for maintaining a clean guide pulley while in use, providing for smooth, consistent and error free speed change, and easily usable with the so-called index shifting systems without the need for constant alignment and adjustment as is the case with the prior art high performance pulleys i.e., those having rigid types of roller bearings. No one has considered that by simply making the teeth of the pulley with a thickness dimension substantially less than the minimum spacing between pairs of opposed roller link plates of the drive chain, the disadvantages heretofore associated and identified with pulleys using rigid high performance bearings would be overcome. Further, no one has realized that the placement of a plurality of apertures concentrically on the pulley would, with rotation in use, promote the clearing of dirt and debris from the pulleys.
The following patents relate to the technology of the present invention but none of them meets the objects of the guide pulley in a manner like that of the instant invention. None of the known prior art have addressed the problems associated with rear derailleur chain guide pulleys.
Essentially all of the patents are of interest only in that they all are
Essentially all of the patents are of interest only in that they all are directed to devices and mechanisms for use with the drive chain system of bicycles. However, none are expressly directed toward defining an improved derailleur pulley for use with bicycle derailleur systems with the construction, objects and advantages of the present invention.
U.S. Pat. No. 3,478,614 discloses a sprocket wheel with a narrow width. U.S. Pat. No. 4,144,773 discloses a sprocket with holes. Finally, U.S. Pat. No. 4,487,088 discloses a sprocket construction for zero catenary chain. Holes or apertures and teeth having narrow thickness are taught for incorporation into the gears of both the crank or front clusters and rear clusters. No one has discovered the advantages of derailleur pulleys having the features of this invention.
There are patents which disclose complicated tooth geometries and complicated slotting schemes to improve the shifting character of the derailleurs for both the front and rear of the multi-speed bicycle. The following patents are listed as representative of the patented prior art.
______________________________________ U.S. PAT. NO. INVENTOR ISSUE DATE ______________________________________ 5,085,620 Nagano 02/04/92 4,813,916 Valin 03/21/89 4,608,878 Shimano 09/02/86 4,526,558 Durham 07/02/85 4,487,088 Olson 12/11/84 4,174,642 Martin et al 11/20/79 4,144,773 Addicks 03/20/79 4,047,603 Ozake 09/13/77 3,478,614 Shimano 11/18/69 ______________________________________